Comparative study on effects of microstructures of hot rolled and twin roll casting 1235 aluminium alloy on surface quality of aluminium foils produced

Abstract

Twin roll casting is an attractive technology for producing aluminium sheets for foils. But, surface defects, such as matte defects, may occur on aluminium foils produced in this way. However, it is not the case on aluminium foils produced by traditional hot rolled process. Optical microscopy, scanning electronic microscopy, energy spectrum and transmission electronic microscopy were used to investigate the effects of the microstructures of the twin roll cast and hot rolled aluminium alloy sheet for foils on the surface defects of the foils produced. It is discovered that central segregation band and surface microsegregation band in twin roll casting aluminium sheet may result in a non-uniformly distributed secondary Al–Fe and Al–Fe–Si particles in workpieces in a lower reduction pass. These non-uniformly distributed Al–Fe and Al–Fe–Si particles and microporosities in a size of several microns generated in solidification process of twin roll casting are the main cause for the surface matte defects of the aluminium foils produced.